The Justice Department is building a massive database that allows state and local police officers around the country to search millions of case files from the FBI, Drug Enforcement Administration and other federal law enforcement agencies, according to Justice officials.

The system, known as "OneDOJ," already holds approximately 1 million case records and is projected to triple in size over the next three years, Justice officials said. The files include investigative reports, criminal-history information, details of offenses, and the names, addresses and other information of criminal suspects or targets, officials said.

The database is billed by its supporters as a much-needed step toward better information-sharing with local law enforcement agencies, which have long complained about a lack of cooperation from the federal government.

But civil-liberties and privacy advocates say the scale and contents of such a database raise immediate privacy and civil rights concerns, in part because tens of thousands of local police officers could gain access to personal details about people who have not been arrested or charged with crimes.

The little-noticed program has been coming together over the past year and a half. It already is in use in pilot projects with local police in Seattle, San Diego and a handful of other areas, officials said. About 150 separate police agencies have access, officials said.

But in a memorandum sent last week to the FBI, U.S. attorneys and other senior Justice officials, Deputy Attorney General Paul J. McNulty announced that the program will be expanded immediately to 15 additional regions and that federal authorities will "accelerate . . . efforts to share information from both open and closed cases."

Eventually, the department hopes, the database will be a central mechanism for sharing federal law enforcement information with local and state investigators, who now run checks individually, and often manually, with Justice's five main law enforcement agencies: the FBI, the DEA, the U.S. Marshals Service, the Bureau of Prisons and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Within three years, officials said, about 750 law enforcement agencies nationwide will have access.

In an interview last week, McNulty said the goal is to broaden the pool of data available to local and state investigators beyond systems such as the National Crime Information Center, the FBI-run repository of basic criminal records used by police and sheriff's deputies around the country.

By tapping into the details available in incident reports, interrogation summaries and other documents, investigators will dramatically improve their chances of closing cases, he said.

"The goal is that all of U.S. law enforcement will be able to look at each other's records to solve cases and protect U.S. citizens," McNulty said. "With OneDOJ, we will essentially hook them up to a pipe that will take them into its records."

McNulty and other Justice officials emphasize that the information available in the database already is held individually by the FBI and other federal agencies. Much information will be kept out of the system, including data about public corruption cases, classified or sensitive topics, confidential informants, administrative cases and civil rights probes involving allegations of wrongdoing by police, officials said.

But civil-liberties and privacy advocates -- many of whom are already alarmed by the proliferation of federal databases -- warn that granting broad access to such a system is almost certain to invite abuse and lead to police mistakes.

Barry Steinhardt, director of the Technology and Liberty Project at the American Civil Liberties Union, said the main problem is one of "garbage in, garbage out," because case files frequently include erroneous or unproved allegations.

"Raw police files or FBI reports can never be verified and can never be corrected," Steinhardt said. "That is a problem with even more formal and controlled systems. The idea that they're creating another whole system that is going to be full of inaccurate information is just chilling."

Steinhardt noted that in 2003, the FBI announced that it would no longer meet the Privacy Act's accuracy requirements for the National Crime Information Center, its main criminal-background-check database, which is used by 80,000 law enforcement agencies across the country.

"I look at this system and imagine it will raise many of the same questions that the whole information-sharing approach is raising across the government," said Marc Rotenberg, executive director of the Electronic Privacy Information Center, a Washington-based group that has criticized many of the government's data-gathering policies.

"Information that's collected in the law enforcement realm can find [its way] into other arenas and be abused very easily," Rotenberg said.

McNulty and other officials said the data compiled under OneDOJ would be subject to the same civil-liberties and privacy oversight as any other Justice Department database. A coordinating committee within Justice will oversee the database and other information-sharing initiatives, according to McNulty's memo.

Gene Voegtlin, legislative counsel for the Arlington-based International Association of Chiefs of Police, said his group welcomes any initiatives to share more data with local law enforcement agencies.

"The working partnership between the states and the feds has gotten much better than the pre-9/11 era," Voegtlin said. "But we're still overcoming a lot of issues, both functional and organizational . . . so we're happy to see DOJ taking positive steps in that area."